1. Field of the Invention
This disclosure generally relates to the field of power generation, and more particularly to power generation in hybrid electric vehicles such as vehicles employing electric machines such as motors and/or generators, in conjunction with engines such as internal combustion engines.
2. Description of the Related Art
Hybrid electric vehicles take a variety of forms, but typically include a power generating device, power storage device, and an electric machine. The power generating device may, for example, take the form of an internal combustion engine. The power storage device may, for example, take the form of an array of chemical battery cells or super- or ultra-capacitors, a flywheel, or other power storage device. The electric machine may take the form of an electric motor and/or generator. For example, the electric machine may take the form of an alternating current (AC) electric motor.
Hybrid electric vehicles may employ a variety of power train architectures. For example, the hybrid electric vehicle may employ a series configuration including a generator that produces power for supply to an electric traction motor and to charge the power storage device. The electric traction motor provides the primary propulsion for the vehicle, and may, for example, be coupled to a set of wheels. Alternatively, the hybrid electric vehicle may employ a parallel configuration that provides the primary propulsion via a direct mechanical connection with an internal combustion engine, as well as via an electric traction motor. Other hybrid electric vehicle power train architectures are known, including combinations of the basic series and parallel architectures discussed above.
A number of approaches have been proposed for generating AC power onboard a hybrid electric vehicle. One approach employs a low power inverter to invert low voltage (e.g., 12V DC) direct current (DC) to alternating current (AC) of an appropriate frequency (e.g., 60 Hz AC). Such an approach is very limited in power output, and adds a large load to the low voltage (e.g., 12V DC) system of the vehicle. Another approach employs an onboard auxiliary generator and a separate secondary internal combustion engine to generate higher levels of AC power. Drawbacks to such an approach include the costs and complexity associated with the additional secondary internal combustion engine. Drawbacks to such an approach also include the low efficiency associated with secondary engines, as well as the minimal accommodations typically made to handle the noise and pollutants produced by secondary engines. A further approach employs an onboard generator driven via a power take off from the primary internal combustion engine. Drawbacks associated with such an approach include the cost and complexity associated with an additional generator. Drawbacks associated with such an approach also include the occupation of a power take off location, as well as the decrease in efficiency attributable to losses associated with the power take off mechanism.
It would be beneficial to produce AC power onboard a hybrid electric vehicle for use when the vehicle is stationary, and/or to produce AC power onboard a hybrid electric vehicle with a minimum of added hardware and other disruption to the hybrid vehicle architecture.